1. Field of the Invention
This invention relates to computer systems and more particularly to power management techniques employed within computer systems.
2. Description of the Relevant Art
An on-going developmental goal of manufacturers has been to reduce the power consumption of computer systems Reducing power consumption typically reduces heat generation of the system, thereby increasing reliability and decreasing costs. In addition, power reduction has been particularly important in maximizing the operating life of battery-powered portable computer systems.
Various techniques have been devised for reducing the power consumption of computer systems. These techniques include increasing the integration of circuitry and incorporation of improved circuitry and power management units (PMU's). One specific power reduction technique involves the capability of stopping clock signals that drive inactive circuit portions such as the microprocessor, a system memory, and a disk controller. A system employing such a technique typically includes a power management unit that detects or predicts when the microprocessor, the system memory, and the disk controller will be inactive, and accordingly stops the clock signals at appropriate times. By turning off "unused" clock signals that drive the inactive circuit portions, overall power consumption of the system is decreased. A similar technique involves removing the power supplied to the microprocessor, the system memory, and the disk controller when they are inactive.
Despite this, conventional computer systems do not remove power from the system oscillators during power management modes. Accordingly, in conventional computer systems, power is wasted when power is applied to the system oscillators when the corresponding clock signals are unused.